Telephone-exchange system.



Patented Aug. 11, 1914.

3 $EEETBSHEET 1.

E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

, APPLIOA-TION FILED NOV. 21, 1905. 1, 1 07, 1 4 1 N v ll" L hN/ w L Q 1 1 5 m? Hm EH-m $3 H & 5& W. 1 1 NM N .Q

ues 50R i @R K Witnesses E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

ABPLIGAIION FILED NOV. 21, 1905.

Patented Aug. 11, 1914.

3 SHEETSSHEET 2.

lvitneowa E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

APPLICATION TILED 11011.21, 1905.

Patented Aug.'11, 1914.

3 SHEETSSHEET 3.

rill

'sraans PATENT orr ou.

EDWARD E. CLEMENT, 0F WASI-IIITGTON,

msrmc'r or COLUMBIA, ASSIGNOR, BY

MESNE ASSIGNMENTS, TO FREDERICK C. STEVENS, 0F ATTICA, NEW YORK.

mower.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at Washington, in the District of Columbia, have invented certain new and useful Im- .provements in Telephone-Exchange Sys-.

terns, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to telephone exchange systems, and has for its ob ect the provision of means for handling the load on the exchange switchboards with greater un1- formity and efficiency than has heretofore been possible,

I attain my object by employing what I may designate as an auxiliary switchboard, which during the busy hour takes care of the overflow from any or all of the main switchboard positions, and during the quiet hours takes care of the entire load, the main switchboard being then put entirely out of serv ce,

It is the object of my present invention particularly to care for the variation in load between operators during the busy hour, by permitting certain conditions to throw anything above a maximum normal load on to an auxiliary switchboard. This may be done by the operators themselves, or it may be done automatically. The latter method will not be specifically claimed herein,- the specific claims in the present case being limited to the manual overflow control. I provide means whereby after the load has fallen to a certain point, connections may be made at all the main board positions to-throw the entire load on the auxiliary board. This board would ordinarily only have a few positions, hence patrolling becomes unnecessary.

My invention is illustrated in theaccompanying drawings, wherein Figure 1 is a diagram showing two subscribers stations with .terminal jacks and signals and an operators cord-circuit on the main switchboard in a central'ofiicc; also a primary selector and a special trunk circuit for throwing calls from the main boa rd to anauxiliary board. Fig. 2 is a similar diagram, complementary to Fig. 1, showing the circuits of the auxiliary board. Fig. 3 is a view .of a modified switch circuit.

I have heretofore spoken of that portion of the equipment which carried the overflow Specification. of Letters Patent.

and the night ,load, as an auxiliary board.

Yate'nted Aug. 11, 1914.

Application filed November 21,1995. Serial No. 288,369.

Before proceeding with the detailed description I wish to state plainly that While i his special section may trulybe called an auxiliary switchboard where it is added to an existing exchange, it can and should quite as truly be called an equalizing section, where it is furnished as part oft-he original equipment. If the main switchboard is a multiple board, this equalizing section may also be equipped uniformly with the rest of the board, although I shall hereinafter describe it as equipped with semi-automatic circuits for connecting lines. The real function of this special section is to provideone definite part of the switchboard equipment which will be complete in itself, and will concen-' trate upon itself the constant wear, which as I have pointed out would otherwise be unequally distributed over the various regular sections of the switchboard.

Referring now to Fig. 1, A' is a subscriber-s station equipped with the usual transmitter, receiver, switch-hook, ringer and condenser. From this substation the line-wires 1 and 2 pass to the contacts n and a of the cut-off relay N, which normally rest against back contacts, connecting the line to the lamp relay M, and the main bat tery B. lVhen the relay N is energized it cuts off the line-relay M and connects the" line through its front contacts to the jacks J, and also to multiple contacts in one or more primary selector switches P to which reference will be made in a moment.

A is another 'subscribers station similar in all respects to the station A, and similarly equipped. Its branches to the primary selector switches are not shown" in full, being indicated only by the stub lines 7 and 8.

The corrcs ionding wires for station A are marked 5 and 6. For interconnecting the lines through the jacks, J J on the main switchboard sections, I provide the usual cord-circuits comprising a pair of plugs, P, P, connected by cord-conductors 9-, 10, 11, 12, and equipped with supervisory lamps, s, 8, controlled by the relays S, S and S, S which are bridged on the main battery B.

So far, the equipment is of a. usual and well-known type, with the addition of the primary selector. The operators or the main switchboard sections use this equip 'ment in the regular way up to the point where they become overloaded, that" is,

where they are forced to lea e calls unanswering and calling plugs P, P each The tip, ring for a purpose which have a tipand sleeve contact onl overflow plug-P however, has and sleeve contacts,

,will appear in connection with the primary and the wires 19'and 21 I the battery and ground,

ing the bridge across the trunk, deiincrgia.

- one side and connected on the other selector operation. The tip of the plug is so made that it may-pass in the jacks, J or J beyond the spring contact, the line-circuit being carried bythe ring and sleeve 2, 10 The incoming trunk jack J 2 on the auxiliary section has three contacts two springs and a sleeve, the answering p lugs On this auxiliary board being therefore three-contact plugs, for convenience in making the cut-off and other controlling connections.

When an operator becomes loaded, and a,

call comes in which she cannot handle she inserts the plug P in the calling line-jack J, continuing the line-circuit as I have said through 15-16, 13-1 1 to the springs of the jack J 2 on the auxiliary board. The relay S and the relay S then act in the same manner as the relays S and S of the ordinary cord-circuit. That is to say, current flows from the main battery through the back contact of relay S by way of wires 17, 18, 1-9, 20, through the sleeve relay S trunk wire 14, and jack wire 16 to the cut-0d relay and ground. lVhen this cntotl" relay pulls up the flow of current continues through the line and back to the ring contact p, the tip side 13 of the trunk, and through relay S to ground, by way of wirc-21 and another back contact of the cut-ofi relay S. Relay S pulls up in series with the line cutoff relay N, and puts battery on the wire 22, the relay S disconnecting wire 22 from the supervisory lamp '8 as long as the subscriber has his phone off the hook. The cutoff relay S is grounded on one side and is connected on the other side by wire 23 to the sleeve contact of the trunk jack J 2 on the auxiliary board. Associated with this trunk-jack is a signal lamp m grounded on through a wire 24 with the wire 22 on the main board, so that when the plug P is inserted in a calling line-jack, and the relay S pulls up in consequence, battery will be put on the wires 22 and 24 to light the lamp. auxiliary board, indicating a call to be answered there. When the answering plug on the auxiliary board is inserted in the jack J battery is thereby put onto the wire 23, whereby the cut-off relay S is, pulled up, disconnecting from m on the magnet.

respectively, break- 3 mg the relays S and S and leaving the talking wires from the line to the jack J absolutely clean and clear. This cut-oil" relay S remains energized as long as the plug is in the trunk-jack on the auxiliary board, and at the same time battery is fed back from the cord-circuit on that board through the trunk-conductor l4 and the line extension 16 to the cut-off relay N to hold it up.

It may well be stated in this connection that while I have shown the line-circuits herein of a standard and well recognized two-wire multiple type, I do not by any means limit myself to such line-circuits, nor to any special cord-circuits. .Line and cutoff relays, with supervisory relays in the cord-circuits, are found in all common buttery systems, and such changes as the addition of contacts in the jacks or of third conductors in the cords, are clearly incidental, so that the circuits I present herein can be changed by any engineer or skilled factory draftsman to suit any particular system to which they are to be applied.

Before passing from Fig. 1 I will briefly describe the primary selector switch P and its connections. This switch is intended to take the place of an answering plug, under certain conditions, to connect any one of a considerable number of lines which may be calling, to the jack J and so to the trunk 131 1 onto the auxiliary'board. The jack J may and will be resorted to by the main board opera-tor, when automatic overflow is desired. Suppose the load has reached the overflow point, the operator can insert the plug P in the jack J and thereby the wires 14, 13 and 25, terminating in the sleeve, ring and tip of the plug, respectively. become extended through the wires 26, 27 and 28 to the contacts 77 p, y) of the switch P This switch has a circular series of contacts, arranged around a central spindle p", which may be constantly rotating, or it may be started to rotate when connection is made with the switch.

The spindle is of steel or iron and forms the core for an electromagnet p, which has an iron head 32 and an iron tubular shell secured to the head, and carrying an armature p at its lower end which is centrally perforated to permit thepassage of the spindle p. On the spindle is rigidly secured a disk 79 having a notch in its upper surface adapted to receive a pin or stud p on the armature p The armature carries a lever p, whose upper end extends into a slot in a tube p fixed radially upon the head of the This tube contains a plug 72 of insulating material, which is adapted to. be slid back and forth in the tube by the armature lever 79, whose upper end is received in an opening in the plug, and plays back and tor-thin the slot in the tube. Mtunted upon the lowerjcm'l of the lever p are I! I0 two inand pi, clish the circuits but as retraction nd plug; in. the t e figure. 'llhese t1 d contacts {1 he former, p is a "llllllllOllS ring, rid the latter p is assowitl' he set of line-contacts in the 1, each of the contacts i when its POtGfitlll is raised by the J of magnet M to permit the ewe energized when it is spring pt, to stick the plug he called the individual ct the lineterminals p l; and trunk terminals 3) agnet p has two windings, n he endc windings, or one outor; sice or the other like the windings of an in a refer-ably put on in layers, o. 1, then a layer oi? No. 2, layers iatedby paper, and the inher ends or both windings grounded on the tubular core. "l

A ie coi e upon which the magnet is wound, is necessarily hollow or tubular, to permit tie passage of the spindle p and the magnet except when locked to the spindle by the pin 7) on its armature, is

3; tire to turn thereon, beingsupported by one I ore studs 31 which take into an annuspindle and turn therein.

to the other winding of t f. lieu a line is calling it is picks up current troin the spied this current passing rough one may winding of 22 and to rough the spindle, energizing the ull' up 'the armature p and the wires 5 and 6 are con- 5' ircs l4r-l3.

n order to hold up the magnet 21) rorid'e he second winding and contact p for each switch. After switch has once stopped to connect a ruler line, the trunk-wire 25 is connect: 2'- h wire 28 and contact 79 to the spring p and the second winding of the This trunk-wire is normally the contactsof relays Sfland S whirh however can put it on hatfirst hy way of wire when the selector l stops, this serving to 1 net p until the auxiliary operator plu s i on the jack J the other we lay S puts hattery on the wire 25 direct, at the sa me that it cuts 0 t thetwo relays S S, the relay S itselfrhecoining;energized only iii pring p is ooi'inected-to one winding outer-1,. g) at that point in the rota-i i sticlnno; the plug 72 between the springer)- when the auxiliary operator plugs in at J T he circuits for these successive steps will be traced in the statement. of operation hereinafter, but it will now be seen that the prirn'ary selector 1, finding a line calling in its rotation, stops with the spring ,0 on the contact 32 of that line, and shoots in the plug 22 thereupon an ell'ect is produced the sameas if a manual plug had been inserted, the relays and N become active, followed by the relay Q", the switch then being held by current through wires and 25. hen theauxiliary operator comes in at J magnot S energized and the further control of the switch is given to the auxiliary operator, through wire 2-3 and, the said relay S,

Referring now to the diagram in Fig. 2, the arrangement ot the switch l1 will be understood from the foregoing statement, read in connection with the following: The magnets f, f and f are controlled by the relays f and f The side switch magnet f" is controlled by the rotary relay f Magnets f and f are merely bridging magnets or choke coils, across the calling end of the switch trunk, included in the connection 30, 31, of the main battery 13, through which talking current is supplied to the called subscriber. The vertical and rotary relays f and f are permanently bridged on the an swerin'g end of the switch trunk, which is separated from the calling end of the concensers G. g is the ringing relay, connected to the last contact point of the side switcher-m f on one side, and to the battery wire 32 on the other. i f, as already stated, is the release magnet, controlledby the relay f which in turn has its circuit closed in either one of two ways, first by both the relays f and f being energized at once, second by being connected to the second point of the side switch-arm f by the relay f" and in response to the last rotary impulse for testing the line wanted after it has been selected.

P and P are the answering and calling plugs, respectively, of a pair on the auxiliary hoard, connected by the conductors 38, 34, and 36, which include the condensers C.

'l'he plug l? has three contacts, a. tip, ring and sleeve, marked p, 72, p The tip and ring are connected to the wires 33 and 35, while the sleeve is cor-inected through wire 37 to a cut-oil or release relay F, thearmature of which is shown as grounded, and normally resting against the terminal of the wires 88 and 39, which are tapped onto the cordconductors 34 and 86'.

Associated with the calling-plug P is a sender, or number transmitter, which I have indicated diagrannna ically at O, with a spindle 0 carrying teeth 0 and 0, cooperat ing with springs '0 these springs beingconnected through wires 4.0 ar d it withthe two cord-conductors 34: and 36, and the spindle being grounded through the wire 42. In operating this form of sender the button 0 is pressed down, and a pin 0 -passing into a slot 0 in the tubular upper end of the spindle 0,. turns the latter so that the teeth 0 do not touch the springs 0 in going down. Incoming back, however, the inner spindle carrying the button 0 is pressed up by a suitable retracting spring not shown, and its first movement upward turns the: sleeve back so that the teeth 0 and 0 turn into contact with the springs 0 I do not of course limit myself to the use of this special sender, as any suitable type may be employed. The idea is that by ressing down the button a greater or less istance any number of impulses up to ten may be sent by the teeth 0 contacting with the spring 40, and always at the end of every set of such impulses a single impulse will be sent by the one tooth 0 In the cord-circuit of. Fig. 2, the relays S and S correspond precisely to the relays S and S in Fig. 1. They jointly control the supervisory lamp s and this lamp indicates to the auxiliary operator-when the calling subscriber has hung up, the control of the connection being given to him. When the plug 1 is thereupon pulled out from the jack- J the relay Filets go and grounds vboth cord-conductors 3d and 36, thereby energizingboth relays f and f of the automatic switch F, which energizes the release relay f and the release magnet f, to restore the switch.

Two points should be distinctly understood here. One is that the employment of the automatic switch F is optional, although I shall claim it. The jack Jpn the auxiliary board, whose trunk wires 43 and 44 pass to the automatic switch F, may be replaced by the multiple jack of a subscribers line. In other words, the automatic switches l contain the multiples of sub- 'scribers lines, which may well be replaced ,by ordinary multiple jacks on the auxiliary board, in such case the sensor 0 being done away with, and each auxiliary operator upon receiving a call trunked from the main switchboard would merely test, plug in and ring in the ordinary way. Suchclaims as I shall make hereinafter covering the combination of the main and auxiliary boards and their working broadly, are intended to include the foregoing or any other arrangement by which the auxiliary operators may have access to the subscribers lines for calling purposes. I prefer automaticswitches however, as shown. P 1

The second point to be understood is this, that while I have shown the control of a semi-automatic connection as being entirely in the hands of the calling subscriber, the auxiliary fol ierat'ors having only what may be called single supervision, nevertheless control can be iron to both of a pair of connected subscrlbers, so that neither can be hung up and prevented by the. other from getting further connections. In order that the called subscriber will release himself, I provide the magnets f and f, in Fig. 2, with. back release contacts, which in series with the contacts of a separate seltlocking relay, control the release magnet f. The self-locking relay pulls up through front contacts of the two relays f and f", or either one of them, or in other words when the called subscriber answers. Being up and locked, this self-locking relay counects the circuit of the magnet f to the back contacts of one -or both of the relays f, 7"", so that when they release their armaturcs upon the called subscriber hanging up, the release magnet will be energized and the switch restored to zero. In such case I provide a. pair of contact springs in the-locking circuit of the selfloeking relay, to be opened by the switch spindle f in its normal or idle position. This arrangement is illustrated in Fig. 3 of the drawings.

The operation of my improved system will be understood from the foregoing description, but may be briefly stated as follows: Assuming that subscriber A desires connection with subscriber A, he removes his receiver from the hook, the lamp m lights, the operator inserts with P, and con:- pletes his connection with J, as usual. Assuming, however, that the operator is already attending to several connections, or has all her cord-circuits busy, upon perceiving the lighting of the lamp m, shc inserts the plug P in the calling line jack, and pays no further attention to it. The insertion of the plug P closes its ring and sleeve p, p on the, spring and sleeve of the jack J, and the eut-oil relay N takes current over the following circuit: B, 18, 19, S 20, l-t,

12 16, N, ground. The relay M'is thereby cut. oil, and the line-wires 1-2 put onto the extensions 15 16 and so onto the trunkwires 1314:. The relay S pulls up in series with the cut-elf relay N, and the relay S now follows. The lamp 8 thereby remains extinguished, but-.it will be observed that when the relay S became energized that a circuit was at once completed for the lampm on the auxiliary switchboard as follows: 13,18, 19, 22, 24-, m and ground. Thereupon the lamp m lights, and the auxiliary operator inserts the plug 1" in jack J The insertion of the plug connects its cord conductors 33 and 35 to the trunkwires l3l4, aml'coilipletes the following eut otl circuit for the relays S in the trunk and F in the cord. B (Fig. 2), l 23"., 72 sleeve of J, 23, S and ground. B th these relays then pull up, the relay S cutting oli the wires '19 and Zl and tluyreby ground.

removing the relays S S from the trunkcircuit, and also breaking the battery connection through wire 19 to wire whereby the lamp m is put out, and the lamp cannot light until the plug P is withdrawn. The ren'ioval of battery from the wire 19 would rlecnergize the cut-oh. relay N of the calling line, except for this fact, that simultaneously with the cutting oif of wire 19, battery is put on through the relay S in Fig. '2 and back through the cord-conductor and the trunk-wire 14 to keep the relay N energized. It will be observed that the trunk circuit after the plug P is inserted perfectly clean and clear, so that the line is really put right on the auxiliary switchboard. Having ascertained the number wanted, the auxiliary operator takes up the plug P and inserts it in a jack J of a hundreds group containing the line wanted. Each connector switch F containing the terminals of one hundred lines, it follows that the trunks from these switches can be grouped by hundreds, and the operator can therefore make one selection by simply plugging into the proper group. Having done so she sends the tens and units number by manipulating the sender 0. Suppose the number of the subscriber wanted was 44-68. She plugs into jack J of group it, and presses down the button to the sixth tooth, which may be indicated by numbers on the stem or in any other suitable way. The button returning completes the following circuit six times: B, 32, f 43, J, I, 34, 40, 0, 0, 42 and ground. The relay f is therel j energized six times, and. closes the following circuit six times: i3, 32, f", f", 45, d6, 47, 48 and Magnet 7 thereupon steps up the wipers f to the 6th row'of linetcontacts. As the button 0" gets to its uppermost position the following circuit is completed, viz. B, 2&2, 7 44, J", 1.,36, 0 0 42 and ground. Relay 7" thereupon closes the circuit of magnet f once as follows: 13, 32, 49, 50, i8 and ground. This opens the wires 45 and 46 and makes a back and forth movement of the escapement which moves the side snitch-arms along one step, whereby magnet f cut off and magnet f is @011.

nccted to wire L5. The operator then presses down key 0 to the eighth tooth, and upon its rising eight vertical impulses over the wires 3 1 and are followed by a single im- )lllsO as before over the wires 36 and M. the eight vibrations of relay f causethe magnet f to step around the wipers f to the eighth contact in the sixth row, which number 68. v A. single impulse over causes relay f to energize f", which pulls up and closes together the test wires 51 and at the contact The idle switch-arm is still. on the Sift cud contact,and during this upward motion of the armature of maguct f the arm remains on this contact, so

that the following circuit is completed to test: B, 32, f 51, a, 52, 7 and to the ti side of Wi')l Now this wi )er is resting on the tip contact of the line wanted. If that line is already busy, there is either a plug in its jack, or some other switch wiper on its tip contact. In the first case there is a ground on the tip side of the line through the relay S of Fig. 1; and in the second place there is a. ground on through the tip wiper f and the magnet, 7', of such a switch as is shown in Fig. In either case, the relay i 1 of the switch with which we aretesting,

pulls up, closing the circuit of the release magnet, which is obvious, so that this magnet instantly releases the switch, which turns back to the beginning of the row and drops its spindle to normal position. It should be observed that this release of the switch is effected beforethe arms of the side switch have gone to the third point, and therefore before any connection has been effected with the line wanted,

It is my intention to have the ringing of the called subscriber made automatic. Assuming that the line wanted is not busy, then there will be no ground on its tip side,

andthe relay 7' will not pull up, so that I the relay f" will let go with the switch re-' maining in position. Upon its letting go, the side switch-arms are all made to take the third step, whereby both magnets f and f are out off, and the wire is connected to the wire 5 L running to the ringing relay 7; the trunk-wires 55 and 56 are connected to their extensions 57 and 58, through the contacts of the ringing relay, and the arm f passes on to its last contact. The ringing relay 9 is thus put into control of the vertical relay 7, and-the ringing may be accomplished in any one ofseveral ways. First, the operator may punch the same button 0* to any indeterminate point, and the consequent impulses will energize the ringing relay g a corresponding number of times to put the generator G on the wipers Second, the operator may have a' button to ground the wire 84 and hold it grounded for the same purpose, or she may press down the button 0* and hold one tooth in contact with the. spring 0 as the button rises. Other means for controlling the "ringing relay or the ringing current, and other methods of starting the same in operation may be employed. These methods of ringing are not essential features of the present invention, although I shall claim automatic ringing, because I plan to save the auxiliary operators the labor of ringing and supervising after completing the connection.

After the subscribers have finished their conversation, and have hung up, the calling subscriber having control of the connection,

go its armature. This closes a circuit from the battery B to the lamp a which lights, amprising the auxiliary operator that disconnection is desired. She thereupon pulls lirst the plug P whereupon the relays S" and F, in Figs. 1 and 2, become deinergized. The former restores current to the lamp s .and the relay S this lamp apprising the main board operator of the desire for, disconnection. The relay F letting go, grounds the wires 3-38 and 3 -39, so that both' relays f and f pull up simultaneously, closing the release circuit through relay f The switch F is thus restored, and as this effect is produced the instant the plug P is pulled, the operator can proceed at once to pull plug P on the auxiliary board. The lamp 8 notifying the main board operator, she withdraws the plug P, and everything is restored to normal.

It will be noticed that after the auxiliary operator. has withdrawn 1 from the jack J that the circuit of lamp or, is again completed until the main board operator has pulled the plug 1 To avoid any danger of false signals, I may provide a separate cut-off relay for this lamp, energized in parallel with the relay S, through the wire 23, and locking itself on the wire 22, this relay bring made more sluggish than the relay S, so that when the plug P is pulled, the locking circuit will be reestablished from the battery B through wire 22, before the relay has time to let go. Then when the plug I is finally pulled, and battery is taken off the wire 22, this relay will have its locking circuit broken, and so let go, again compl'eh ing the circuit of lamp m through the wire 2t ready for another advanced signal.

The foregoing action depends upon the inain' board operator sticking the plug P I may, however, through the primary selector P do the same thing automatically. \Vhen the load curve has risen to a predetermined point, the main board operators may insert their plugs 1 leave them there. The spindle p of each primary selector is supposed then to be turning, controlled in common by the lines in its group, through their line relays M or in any other satisfactorymanner. Suppose line A calls. The lamp m will light, and at the same time the contacts 2 of the line in all of the primary selector switches will have their potential raised. The operator being busy, the first primary selector that reaches a line contact 7') gets a completed circuit as follows: 13, 17, (30, 61, p, p, winding of p and ground. This energizes the core, spindle and shell of 71 and causes the armature p to be pulled up, pulling the stud 72 out of its socket in the collar p, throwing forward the lever pushing the plug 72 into the individual line-jack through the opening p in the jack ring,

"When the plug P of the auxiliary in the jacks J and and spreading the springs p 72" into con tact with the springs p, 7), thus connecting the wires 26 and 27 with the line extensions 5-6. Since the wire 26 is already connected through the jack and plug J. 1", respectively, to the wire 14, the effect of the insertion of plug 72 is toconnect the trunk 13l4t to the linejust the same as though the plug P had been put in tln jack J. In other words, current flows from the battery B, through the relay S to the sleeve side 6 and so to the cut-off relay N, which puts the line-wires l-2 on the extensions S -G, and cuts off current from the relay M which in turn cuts off current from the lamp m and the wire 61. Theline contacts p there fore become dead again the instant any arm picks up the line, so that no other of the primary selectors will get on the same line.

The instant thcline is put on the wires 5(3 current flows back through wires 1, 5 and 27 to the trunk wire 13 and relay S, which puts battery current from the wire 22 onto the wire 25, and so by way of the tip 7) and the wire 28 to the ring contact 2 of the primary selector in use, continuing a locking circuit therefor through the springs yr, the second winding of magnet 71, and ground. opcra tor is inserted in the jack J current is maintained on the wire for this same purpose through the wire 18 controlled by the relay S", and it will be observed that the further operation on the part of the auxiliary operator, and the control by the calling subscriber, arc the same step-by-stcp as those which I have described before. When the plug p of the primary selector switch goes into a calling line-jack, it puts the line through on the trunk and (he llow of current through relay S lights the lamp 1 by putting battery on the wire 2i. It is thought that the subsequent steps need not be rccapitulated, as they will be sufficiently understood from the previous statement o l' operation. l

Having thus described my invention, what I claim and desire to secure by Letters Patent is: 115

1. In a telephone exchange syslem, sub-=l scribers lines, a main switchboard having subscribers calling and answering terminals, an auxiliary switchboard having trunk terminals and subscribers calling terminals only, connective trunks between said main switchboard and said auxiliary switchboard, automatic means at the main switchboard for trunking calls to the auxiliary switchboard and means at the latter board for answering the calls and making the connections desired.

2. In a telephone exchange system a main switchboard and an auxiliary switchboard, means for receivin and answering calls and all) making conm-etioi'is on the main switch board, a trunk line ha ring, automatic switching. means controlled at the main switchboard and adapted when active to pick up the calling subscribers lines, said trunlcline also having a connection terminal on the auxiliary board, whereby any call thus picked up may be answered, and means on the auxiliary board for completing the con nectii'ins desired.

3. In a telephoneexchange system a main switchboard and an auxiliary board, answering and connecting apparatus at the main switchboard for all the lines, trunk lines between the main board and the auxiliary board, each trunk line having a primary selector switch containing subscribers line tern'iinals in multiple with those on the main board, and each trunk also having an answering terminal on the auxiliary board,

whereby calls may be answered and connections completed thereat.

A. In a telephone exchange system a plurality of subscribers lines, a ll'lillItSWltCllboard equipped with a'manual connecting; apparatus, and auxiliary automatic connecting means adapted to be set upon the occurrence of an overload on the main switchboard, to respond to calls over the subscribers lines, and thereupon to select and-eiiect initial connection 'of said lines apart from the main switchboard.

In a telephone'exchange system, a main switchboard having manual answering and connecting terminals, an auxiliary switchboard having automatically actuated switching means for answering calls over the same subscribers lines, connecting means associated therewith, operators controlling means therefor, andautomatic releasing means for the wnnecting means.

6. In a telephone exchange system, a main switchboard containing the terminals of subscribers lines and provided with manual means for answering calls and completing connections over the same, an auxiliary switchboard, automatic selector switches containing line terminals for trunking calls from said lines to the auxiliary board, and

means controlled at the main board for rendering said switches active.

7. In a telephone exchange system, a main switchboard equipped with manual answer ing devices and connective apparatus and an auxiliary switchboard having auto natic line seeking switches containing line multiples for answering and switching overliow calls from the .inanua'l board.

8. In a telephone exchange system subscribers answering terminals and operators connective circuits adapted to connect the subscribers lines with automatic connector switches, an operatofs sender associated with the connective circuits to operate the switches, and means actuated in eii'ecting disconnection from the calling line to release the 'connectirg; switch in any case and so clear the called line.

9. In a telephone exchange system calling line-terminals as J, operators answering plugs as lflronnections from said plugs to automatic switches as l an operators sender O, and means as 1*" associated with each answering plugr P for releasing and restoring the automatic switching apparatus upon the plug being disconnected from the calling line terminal.

10. in; a telephone exchange system, a main switchboard provided with subscribers multiple line terminals, means for answering calls, an auxiliary switchboard, line seeking switches automatically controlled for trunkinn calls thereto and means controlled by the auxiliary operator for eilecting the coin plcted connection.

11. in atelephone exchange system, subscribers lines, a main switchboard and an auxiliary switchboard, means at said mainv switchboard for answering calls and for completing connections, and additional line seek ing means for transferring calls to said has iliary switchboard, automatic switches adapted to eifect a connection with a called.

subscribers line and means at the auxiliary board for controlling said automatic switehes- In testimony whereof I aiiix my signature in presence of two witnesses.

EDWARD CLEMENT.

Witnesses:

JAMES H. Maria,

E. EnMoNsTon, J r. 

